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What is Unix ?

The UNIX operating system is a set of programs that act as a link between the computer and the user.

• Unix was originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna.
• There are various Unix variants available in the market. Solaris Unix, AIX, UP Unix and BSD are few examples. Linux is also a flavour of Unix which is freely available.
• Several people can use a UNIX computer at the same time; hence UNIX is called a multiuser system.
• A user can also run multiple programs at the same time; hence UNIX is called multitasking.

Login Unix:

You can login to the system using login command as follows:

login : amrood
amrood's password:
Last login: Sun Jun 14 09:32:32 2009 from 62.61.164.73
[amrood]$

Logging Out:

When you finish your session, you need to log out of the system to ensure that nobody else accesses your files while masquerading as you.

To log out:

1. Just type logout command at command prompt, and the system will clean up everything and break the connection

File Management:

In UNIX there are three basic types of files:

1. Ordinary Files: An ordinary file is a file on the system that contains data, text, or program instructions. In this tutorial, you look at working with ordinary files.
2. Directories: Directories store both special and ordinary files. For users familiar with Windows or Mac OS, UNIX directories are equivalent to folders.
3. Special Files: Some special files provide access to hardware such as hard drives, CD-ROM drives, modems, and Ethernet adapters. Other special files are similar to aliases or shortcuts and enable you to access a single file using different names.

Filename Substitution:

Filename Manipulation:

Directory Management:

Environment Setup:

When you type any command on command prompt, the shell has to locate the command before it can be executed. The PATH variable specifies the locations in which the shell should look for commands.

PS1 and PS2 Variables:

The characters that the shell displays as your command prompt are stored in the variable PS1.

When you issue a command that is incomplete, the shell will display a secondary prompt and wait for you to complete the command and hit Enter again. The default secondary prompt is > (the greater than sign), but can be changed by re-defining the PS2 shell variable:

Escape Characters:

Environment Variables:

Following is the partial list of important environment variables. These variables would be set and accessed as mentioned above:

Filters & Pipes:

Special Variables

Shell Basic Operators

Arithmetic Operators:

Assume variable a holds 10 and variable b holds 20 then:

Relational Operators:

Assume variable a holds 10 and variable b holds 20 then:

Boolean Operators:

Assume variable a holds 10 and variable b holds 20 then:

String Operators:

Assume variable a holds “abc” and variable b holds “efg” then:

File Test Operators:

Assume a variable file holds an existing file name “test” whose size is 100 bytes and has read, write and execute permission on:

Shell Decision Making

The if…fi statement:

if [ expression ]
then
   Statement(s) to be executed if expression is true
fi

The if…else…fi statement:

if [ expression ]
then
   Statement(s) to be executed if expression is true
else
   Statement(s) to be executed if expression is not true
fi

The if…elif…fi statement:

if [ expression 1 ]
then
   Statement(s) to be executed if expression 1 is true
elif [ expression 2 ]
then
   Statement(s) to be executed if expression 2 is true
elif [ expression 3 ]
then
   Statement(s) to be executed if expression 3 is true
else
   Statement(s) to be executed if no expression is true
fi

The case…esac Statement:

case word in
  pattern1)
     Statement(s) to be executed if pattern1 matches
     ;;
  pattern2)
     Statement(s) to be executed if pattern2 matches
     ;;
  pattern3)
     Statement(s) to be executed if pattern3 matches
     ;;
esac

Shell Loop Types:

The while Loop:

while command
do
   Statement(s) to be executed if command is true
done

The for Loop:

for var in word1 word2 ... wordN
do
   Statement(s) to be executed for every word.
done

The until Loop:

until command
do
   Statement(s) to be executed until command is true
done

The select Loop:

select var in word1 word2 ... wordN
do
   Statement(s) to be executed for every word.
done

Shell Loop Control:

The break statement:

break [n]

The continue statement:

continue [n]

Shell Substitutions:

The shell performs substitution when it encounters an expression that contains one or more special characters.

Command Substitution:

The command substitution is performed when a command is given as:

`command`

Variable Substitution:

Here is the following table for all the possible substitutions:

Redirection Commands:

Following is the complete list of commands which you can use for redirection:

Shell Man Pages Help:

This quick guide lists commands, including a syntax and brief description. For more detail, use:

$man command

$man command

Files and Directories:

These commands allow you to create directories and handle files.

Manipulating data:

The contents of files can be compared and altered with the following commands.

Compressed Files:

Files may be compressed to save space. Compressed files can be created and examined:

Getting Information:

Various Unix manuals and documentation are available on-line. The following Shell commands give information:

Network Communication:

These following commands are used to send and receive files from a local UNIX hosts to the remote host around the world.

Some of these commands may be restricted at your computer for security reasons.

Messages between Users:

The UNIX systems support on-screen messages to other users and world-wide electronic mail:

Programming Utilities:

The following programming tools and languages are available based on what you have installed on your Unix.

Misc Commands:

These commands list or alter information about the system:

Get PayBox Debit Card & earn money

In ubuntu you need to install system as a non root user
then login as that user, and if you want to run commands then you need to type sudo at the beginning of the command to gain root access to execute that command.

it is a hassle for sure, to avoid it you have 3 options

1. login as your username/pass, then
:~$ sudo passwd root
Password:<type your password>
Enter new UNIX password:<type new root password>
Retype new UNIX :<type new root password again>

then logout and login as root.

or, second option is

2. login as your user/pass then do

$ sudo -i

Above command will start /bin/bash as a root shell so that you can enter a root user command without using sudo command.

o, third option is

3. run shell as root user:
$ sudo bash
OR
$ sudo -s
Supply your password and you will become a root user.
if you want then you can put it in .profile or /etc/profile as a permanent solution( not recommended though)

cheers

Jamal

Work precedence:

1. /etc/hosts.allow-
   1. if allow will not check 2
   2. if not found then go to 2
2. /etc/hosts.deny .
   1. if not found allow access.

Points to remember

• You can have only one rule per service in hosts.allow and hosts.deny file.
• Any changes to hosts.allow and hosts.deny file takes immediate effect.
• The last line in the files hosts.allow and hosts.deny must be a new line character. Or else the rule will fail.

Rule Syntax
The syntax for both hosts.allow and hosts.deny file takes the following form:

daemon : client [:option1:option2:...]

Examples

Allow SSH

for xyz.com and

deny access to all the others.

sshd : .xyz.com

… and in the hosts.deny file I include the rule:

sshd : ALL

Denys FTP access to all in abc.com domain  and hosts in the 192.168.1.0 network.

#FILE: /etc/hosts.deny
vsftpd : 192.168.1. , .abc.com

Beautification

#FILE: /etc/hosts.deny
vsftpd : 192.168.1. , .abc.co.in : spawn /bin/echo  `/bin/date` access denied >> /var/log/vsftpd.log : deny

In the above rule, spawn logs a message to the vsftpd log file each time the rule matches. deny is optional if you are including this rule in the hosts.deny file.

For example, you can use spawn option to send mail to the admin when ever a deny rule is matched.

Wildcards

You can use wildcards in the client section of the rule to broadly classify a set of hosts. These are the valid wildcards that can be used.

• ALL – Matches everything
• LOCAL – Matches any host that does not contain a dot (.) like localhost.
• KNOWN – Matches any host where the hostname and host addresses are known or where the user is known.
• UNKNOWN – Matches any host where the hostname or host address are unknown or where the user is unknown.
• PARANOID – Matches any host where the hostname does not match the host address.

Patterns

ALL : 123.12.

Matches all the hosts in the 123.12.0.0 network. Note the dot (.) in the end of the rule.

ALL : 192.168.0.1/255.255.255.0

IP address/Netmask can be used in the rule.

sshd : /etc/sshd.deny

If the client list begins with a slash (/), it is treated as a filename. In the above rule, TCP wrappers looks up the file sshd.deny for all SSH connections.

sshd : ALL EXCEPT 192.168.0.15

will allow ssh connection for only the machine with the IP address 192.168.0.15 and block all other connections.

You can use the options allow or deny to allow or restrict on a per client basis in either of the files hosts.allow and hosts.deny

in.telnetd : 192.168.5.5 : deny
in.telnetd : 192.168.5.6 : allow

Shell Commands

As mentioned above, you can couple the rules to certain shell commands by using the following two options.

spawn – This option launches a shell command as a child process. For example, look at the following rule:

sshd : 192.168.5.5 : spawn /bin/echo `/bin/date` from %h >> /var/log/ssh.log : deny

Each time the rule is satisfied, the current date and the clients hostname %h is appended to the ssh.log file.

twist – This is an option which replaces the request with the specified command. For example, if you want to send to the client trying to connect using ssh to your machine, that they are prohibited from accessing SSH, you can use this option.

sshd : client1.xyz.com : twist /bin/echo “You are prohibited from accessing this service!!” : deny

When using spawn and twist, you can use a set of expressions. They are as follows :
%a — The client’s IP address.
%A — The server’s IP address.

%c — Supplies a variety of client information, such as the username and hostname, or the username and IP address.

%d — The daemon process name.
%h — The client’s hostname (or IP address, if the hostname is unavailable).
%H — The server’s hostname (or IP address, if the hostname is unavailable).

%n — The client’s hostname. If unavailable, unknown is printed. If the client’s hostname and host address do not match, paranoid is printed.

%N — The server’s hostname. If unavailable, unknown is printed. If the server’s hostname and host address do not match, paranoid is printed.

%p — The daemon process ID.

%s — Various types of server information, such as the daemon process and the host or IP address of the server.

%u — The client’s username. If unavailable, unknown is printed.

1. install wine1.2-gecko(or latest)

apt-get install wine1.2-gecko

this should enable you to run general windows based softwares.
to run msoffice or enterprise applications which uses .net frameworks/msxml/etc you have to do the followings

2. download winetricks

wget http://www.kegel.com/wine/winetricks

then install the updates:

chmod +x ./winetricks

./winetricks gdiplus riched20 riched30 msxml3 msxml4 msxml6 corefonts tahoma vb6run vcrun6 msi2

sudo apt-get install wine cabextract

then run msoffice2007 setup.

**
i couldnt run office outlook 2007.
but msword/excel/power point runs.

To remove wine:
sudo apt-get –purge remove wine

Cheers

Jamal